Flexible multi-channel wireless audio receiver system

ABSTRACT

A flexible multi-channel diversity wireless audio receiver system for routing, processing, and combining multiple radio frequency (RF) signals containing audio signals received on respective antennas is provided. The wireless audio receiver system provides flexible routing of multiple RF signals in different selectable modes, and low latency uninterrupted reception of signals in harsh RF environments by combining multiple RF signals to maximize signal-to-noise ratio. The audio output may be generated in an uninterrupted fashion and mitigate multipath fading, interference, and asymmetrical noise issues. Received RF signals may also be cascaded by the wireless audio receiver system to allow daisy chaining.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/605,497, filed on May 25, 2017, which is a divisional of U.S. patentapplication Ser. No. 14/846,373, filed on Sep. 4, 2015, the contents ofboth which are fully incorporated herein by reference.

TECHNICAL FIELD

This application generally relates to a flexible multi-channel wirelessaudio receiver system. In particular, this application relates to amulti-channel diversity wireless audio receiver system for routing,filtering, processing, and combining multiple radio frequency (RF)signals containing audio signals received on respective antennas.

BACKGROUND

Audio production can involve the use of many components, includingmicrophones, wireless audio transmitters, wireless audio receivers,recorders, and/or mixers for capturing, recording, and presenting thesound of productions, such as television programs, newscasts, movies,live events, and other types of productions. The microphones typicallycapture the sound of the production, which is wirelessly transmittedfrom the microphones and/or the wireless audio transmitters to thewireless audio receivers. The wireless audio receivers can be connectedto a recorder and/or a mixer for recording and/or mixing the sound by acrew member, such as a production sound mixer. Electronic devices, suchas computers and smartphones, may be connected to the recorder and/ormixer to allow the crew member to monitor audio levels and timecodes.

Wireless audio transmitters, wireless audio receivers, wirelessmicrophones, and other portable wireless communication devices includeantennas for transmitting and receiving radio frequency (RF) signalswhich contain digital or analog signals, such as modulated audiosignals, data signals, and/or control signals. Users of portablewireless communication devices include stage performers, singers,actors, news reporters, and the like.

A wireless audio transmitter may transmit an RF signal that includes anaudio signal to a wireless audio receiver. The wireless audiotransmitter may be included in a wireless handheld microphone, forexample, that is held by the user and includes an integrated transmitterand antenna. When the RF signal is received at the wireless audioreceiver, the RF signal may be degraded due to multipath fading causedby constructive interference and/or by other types of interference. Thisdegradation may cause the RF signal to have a poor signal-to-noise ratio(SNR), which can result in bit errors that can cause audio artifacts andmuting of the resulting output audio. However, muting the output audiois undesirable in many situations and environments, such as duringprofessional stage productions and concerts. The effects of suchmultipath fading and interference are most prevalent in harsh RFenvironments where physical and electrical factors influence thetransmission and reception of RF signals, e.g., movement of themicrophone within the environment, other RF signals, operation in largevenues, etc.

To alleviate issues with multipath fading of RF signals, wireless audiocomponents may utilize frequency diversity and/or antenna diversitytechniques. In particular, wireless audio transmitters may utilizefrequency diversity to simultaneously transmit on one antenna two RFsignals of two separate frequencies in a combined RF signal, where thetwo RF signals both include the same audio signal. A wireless audioreceiver may then use one or both of the underlying RF signals. Inaddition, wireless audio receivers may utilize antenna diversity tosimultaneously receive RF signals from a wireless audio transmitter onmultiple antennas. The received RF signals can be combined to produce asingle audio output.

In some cases, a two antenna system may not be sufficient to provideadequate performance. More than two antennas may be desired in order tobenefit from the user of antennas with different directional gains sothat the coverage of the wireless system is extended. For example, aparticular venue may have multiple “zones” that need to be covered by asingle wireless receiver and/or a venue may be very large. In thesesituations, having more than two antenna locations may result inimproved coverage and reduced transmitter to antenna distances. As such,a traditional two antenna diversity may not provide adequateperformance.

When utilizing frequency diversity and/or antenna diversity techniques,existing wireless audio receivers typically combine multiple RF signalsreceived on multiple antennas by scaling each RF signal proportionallyusing maximal-ratio combining (MRC) under the assumption that there isequal noise power in each RF signal. However, if the antennas aresubjected to asymmetrical noise, e.g., when one antenna is closer to asource of interference, then MRC does not maximize the signal-to-noiseratio of the combined signal. This can cause the receiver to producenon-optimal audio output, such as degraded sound or muting. In addition,existing wireless audio receivers may need additional components andcomplex arrangements in certain situations and environments. Forexample, if more than two antennas are utilized, external antennascombiners and external switches may be needed.

Accordingly, there is an opportunity for a multi-channel wireless audioreceiver system that addresses these concerns. More particularly, thereis an opportunity for a multi-channel diversity wireless audio receiversystem that provides flexible routing of multiple RF signals indifferent selectable modes, and low latency uninterrupted reception ofsignals in harsh RF environments by combining multiple RF signals tomaximize signal-to-noise ratio. Furthermore, there is an opportunity fora multi-channel diversity wireless audio receiver system that providesperformance benefits when high-order modulation scheme (such as 16-QAMand 64-QAM) are utilized that have higher RF sign-to-noise ratiorequirements.

SUMMARY

The invention is intended to solve the above-noted problems by providingmulti-channel wireless audio receiver systems and methods that aredesigned to, among other things: (1) flexibly route multiple RF signalsto different RF analog processing modules in different selectable modes;(2) maximize the SNR of a combined signal by combining multiple RFsignals by scaling them proportionally to their respective SNR; (3)cascade received RF signals to allow daisy chaining of receivers; (4)enable the allocation of additional, redundant channels of RF processingto additional antenna inputs for mission critical audio sources; and (5)enable the allocation of fewer RF processing channels to a given audiochannel to maximize the number of audio channels that can be decoded.

In an embodiment, a wireless audio receiver includes a mode selectioninterface for enabling a user to select one of a plurality of modes ofthe wireless audio receiver; a plurality of radio frequency (RF) portseach configured to receive a plurality of RF signals from a respectiveantenna, wherein each of the plurality of RF signals comprises one ormore audio signal; and an antenna distribution module in communicationwith the plurality of RF ports. The antenna distribution module may beconfigured to when in a first mode, route the plurality of RF signals toone or more of a plurality of downstream processing components; and whenin a second mode, route a first subset of the plurality of RF signals tobe output on a first subset of the plurality of RF ports and route asecond subset of the plurality of RF signals to one or more of theplurality of downstream processing components.

In another embodiment, a wireless audio receiver includes a firstplurality of radio frequency (RF) ports each configured to receive afirst plurality of RF signals from a respective antenna; a secondplurality of RF ports each configured to receive a second plurality ofRF signals from a respective antenna and further configured to outputone of the first plurality of RF signals based on a mode of the wirelessaudio receiver, wherein each of the first and second pluralities of RFsignals comprises one or more audio signals; a first plurality ofantenna distribution modules each associated with each of the firstplurality of RF ports; and a second plurality of antenna distributionmodules each associated with each of the second plurality of RF ports.The first plurality of antenna distribution modules may each include afirst splitter in communication with one of the first plurality of RFports, the first splitter for splitting one of the first plurality of RFsignals into a first plurality of split RF signals, wherein the firstplurality of split RF signals are routed to one or more of a pluralityof downstream processing components, a first switch, and a secondswitch; and the first switch in communication with the first splitterand one or more of the plurality of downstream processing components,the first switch for switching between one of the first plurality ofsplit RF signals and one of a second plurality of split RF signals. Thesecond plurality of antenna distribution modules may each include thesecond switch in communication with one of the second plurality of RFports and the first splitter, the second switch for switching betweenone of the first plurality of split RF signals and one of the secondplurality of RF signals; and a second splitter in communication with thefirst switch and the second switch, the second splitter for splittingone of the second plurality of RF signals into a second plurality ofsplit RF signals, wherein the second plurality of split RF signals arerouted to the first switch.

In a further embodiment, a method of combining a plurality of digitalmodulated signals (y) based on a signal-to-noise ratio (SNR) of each ofthe plurality of digital modulated signals is described. The pluralityof digital modulated signals may be respectively derived from aplurality of received radio frequency (RF) signals each comprising adigital audio bit stream representing an audio signal. The method mayinclude deriving a channel estimate (h) of each of the plurality ofdigital modulated signals; measuring a normalized noise power (σ²) ofeach of the plurality of digital modulated signals; deriving anormalized received signal based on the channel estimate; and combiningthe plurality of digital modulated signals to produce a combinedmodulated signal based on the normalized noise power and the normalizedreceived signal.

These and other embodiments, and various permutations and aspects, willbecome apparent and be more fully understood from the following detaileddescription and accompanying drawings, which set forth illustrativeembodiments that are indicative of the various ways in which theprinciples of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless audio receiver system, inaccordance with some embodiments.

FIG. 2 is a schematic diagram of an antenna distribution module for usein the wireless audio receiver system of FIG. 1, in accordance with someembodiments.

FIG. 3 is a schematic diagram of RF analog processing modules for use inthe wireless audio receiver system of FIG. 1, in accordance with someembodiments.

FIG. 4 is a schematic diagram of the components of each of the RF analogprocessing paths of the RF analog processing modules of FIG. 3, inaccordance with some embodiments.

FIG. 5 is a schematic diagram of a digital signal processing module foruse in the wireless audio receiver system of FIG. 1, in accordance withsome embodiments.

FIG. 6 is a flowchart illustrating operations for combining multipledigital modulated signals into a single combined signal using thewireless audio receiver system of FIG. 1, in accordance with someembodiments.

FIG. 7 is a schematic diagram of a digital signal processing module foruse in the wireless audio receiver system of FIG. 1, in accordance withsome embodiments.

DETAILED DESCRIPTION

The description that follows describes, illustrates and exemplifies oneor more particular embodiments of the invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in such a way to enable one of ordinaryskill in the art to understand these principles and, with thatunderstanding, be able to apply them to practice not only theembodiments described herein, but also other embodiments that may cometo mind in accordance with these principles. The scope of the inventionis intended to cover all such embodiments that may fall within the scopeof the appended claims, either literally or under the doctrine ofequivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers, such as, for example, in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. Such labeling and drawing practices do not necessarilyimplicate an underlying substantive purpose. As stated above, thespecification is intended to be taken as a whole and interpreted inaccordance with the principles of the invention as taught herein andunderstood to one of ordinary skill in the art.

The flexible multi-channel wireless audio receiver system describedherein can flexibly route multiple received RF signals to different RFanalog processing modules in various selectable modes, and combine themultiple received RF signals into a combined signal with maximized SNR,while processing the signals with low latency to generate an outputaudio signal in an uninterrupted fashion. The receiver may furthereliminate the need for external antennas combiners and manual switchingbetween multiple antennas while being housed in a single receiver formfactor. In particular, the receiver may have a variety of differentmodes that allow different numbers of antennas to be used, depending onthe desired application and environment the receiver is being used in.

For example, in one scenario, the receiver may be connected to fourantennas that cover the same space (e.g., a large stage or venue) forimproved coverage. In another scenario, the receiver may be connected totwo pairs of antennas, where each pair of antennas covers a differentspace (e.g., two parts of the venue that can be divided), such thatperipheral spaces like backstage or dressing rooms are also covered. Ina further scenario, the receiver may be connected to additional antennasto allow coverage of irregularly-shaped performance areas (e.g.,jutting/thrusting stages or venues with secondary stages) where optimalcoverage with a single pair of antennas is not possible. In anotherscenario, the receiver may be connected to multiple pairs of antennas tobe deployed as “cold backups” for use when a performance issue isidentified. Typically, in this case, a skilled operator must manuallydetect the issue and intervene to engage the “cold backups”. However,the receiver described herein can make use of the “cold backup” antennasin a dynamic and automated manner.

FIG. 1 is a schematic diagram of a wireless audio receiver 100 forreceiving one or more radio frequency (RF) signals containing digitalaudio bit streams that represent audio signals. The receiver 100 mayinclude multiple RF ports 102 a-d that can be connected to respectiveantennas to receive RF signals. The RF ports 102 a-d may include asubset of ports that can be configured to be used for cascading purposesto daisy chain the receiver 100 to other wireless receivers. Inparticular, as seen in FIG. 1, the RF ports 102 a, 102 b (labeled Ant Aand Ant B, respectively) are configured to be connected to separateantennas (not shown) that each receive an RF signal. The RF ports 102 c,102 d (labeled Ant C/Cascade A and Ant D/Cascade B, respectively) can beconfigured to be connected to separate antennas (not shown) that eachreceive an RF signal as well, or the RF ports 102 c, 102 d can beconfigured to output the RF signals received on the RF ports 102 a, 102b, respectively. As such, the RF ports 102 a-d of the receiver 100 canbe connected to two, three, or four antennas, depending on the needs ofa user. It should be noted that although FIG. 1 shows four ports 102 a-dfor connecting up to four antennas, the receiver 100 is extensible tomore than four ports and antennas. Various components included in thewireless audio receiver 100 may be implemented using software executableby one or more servers or computers, such as a computing device with aprocessor and memory, and/or by hardware (e.g., discrete logic circuits,application specific integrated circuits (ASIC), programmable gatearrays (PGA), field programmable gate arrays (FPGA), etc.

The RF signals may be received at the receiver 100 from a wireless audiotransmitter and/or a microphone, for example, that has captured thesound of a production or other audio source. A user may select variousmodes of the receiver 100 depending on how many antennas are connectedto the ports 102 a-d and may denote the number of RF signals beingreceived. The selected mode of the receiver 100 may determine how thereceived RF signals are switched by an antenna distribution module 104,as described below. The modes of the receiver 100 may include being ableto select how many ports 102 a-d are utilized and being able to selectwhether the received RF signals have utilized frequency diversity orantenna diversity.

One mode of the receiver 100 includes being able to select whetherseveral of the RF ports (e.g., RF ports 102 c, 102 d) are used to outputincoming RF signals to other receiver(s), also known as cascade mode. Inthis mode, multiple RF signals (including audio signals) that have beentransmitted may be received and processed by the receiver 100 and arealso output to other receivers for daisy chaining purposes. For example,two ports (e.g., RF ports 102 a, 102 b) may be respectively connected totwo antennas to receive four transmitted RF signals each including anaudio signal from a single audio source. The four RF signals may havebeen transmitted using frequency diversity on four differentfrequencies. One audio output signal may be generated in this case bycombining the four received RF signals. As another example, two ports(e.g., RF ports 102 a, 102 b) may be respectively connected to twoantennas to receive a single transmitted RF signal including an audiosignal from a single audio source. The single transmitted RF signal maybe received by the two antennas of the receiver 100 to take advantage ofantenna diversity. One audio output signal may be generated in this caseby combining the RF signal received on the two antennas.

Another mode of the receiver 100 includes being able to select whetherseveral of the RF ports (e.g., RF ports 102 c, 102 d) are connected tomore antennas (e.g., antennas Ant C/Cascade A and Ant D/Cascade B),rather than being output as in the cascade mode described above. In thismode, fewer audio channels that have been transmitted may be received bythe receiver 100 but these audio channels may be processed by redundantRF analog processing modules 106 a-d. For example, four ports (e.g., RFports 102 a-d) may be respectively connected to four antennas to receivea single transmitted RF signal including an audio signal from a singleaudio source. The single transmitted RF signal may be received by thefour antennas of the receiver 100 to take advantage of antennadiversity. One audio output signal may be generated in this case bycombining the RF signal received on the four antennas. As anotherexample, four ports (e.g., RF ports 102 a-d) may be respectivelyconnected to four antennas to receive two transmitted RF signals, whereeach transmitted RF signal has been transmitted at different frequenciesand includes a unique audio signal from a unique audio source. In thisexample, two audio output signals may be generated by respectivelycombining the RF signals received on the four antennas. Four of the RFsignal processing paths (described further below) may be utilized andcombined to create one of the audio output signals, while the other fourRF signal processing paths may be utilized and combined to create theother audio output signal. As a further example, four ports (e.g., RFports 102 a-d) may be respectively connected to four antennas to receivetwo transmitted RF signals each including an audio signal from a singleaudio source. The two RF signals may have been transmitted usingfrequency diversity on two different frequencies. One audio outputsignal may be generated in this case by combining the two received RFsignals. All of the RF signal processing paths 302 a, 302 b, 304 a, 304b, 306 a, 306 b, 308 a, 308 b (described further below) may be utilizedand combined to create the one audio output signal.

In certain modes, the receiver 100 includes an antenna distributionmodule 104 that can flexibly route the RF signals received on the RFports 102 a-d to RF analog processing modules 106 a-d (denoted in FIG. 1as RF Channels 1-4). In addition, if the receiver 100 is being used in acascade mode for daisy chaining to another receiver, the antennadistribution module 104 can take the RF signals received on RF ports 102a, 102 b (Ant A and Ant B), route the RF signals to RF analog processingmodules 106 a-d (RF Channels 1-4), and also route the RF signals to beoutput on RF ports 102 c, 102 d (Ant C/Cascade A and Ant D/Cascade B).The antenna distribution module 104 may also process the received RFsignals prior to routing the RF signals to the RF analog processingmodules 106 a-d and/or to the RF ports 102 c, 102 d. Further details ofthe antenna distribution module 104 are described below with respect toFIG. 2.

The RF analog processing modules 106 a-d may receive the routed RFsignals from the antenna distribution module 104 and generate analogmodulated signals that have been shifted to an intermediate frequency(IF). Each RF analog processing modules 106 a-d may include two parallelRF signal processing paths for processing the routed RF signals, asdescribed in more detail with respect to FIG. 3.

The analog modulated signals may be converted to digital modulatedsignals by analog to digital converters (ADC) 108 a-d. The digitalmodulated signals may be received by a digital signal processing (DSP)module 110 and demodulated to generate up to four digital audio signalsthat can be output from the receiver 100. Digital to analog converters(DAC) 112 a-d may also convert the digital audio signals to respectiveanalog audio signals to be output from the receiver 100. In embodiments,the DSP module 110 may combine the digital modulated signals from theADCs 108 a-d into a combined modulated signal, based on thesignal-to-noise ratios (SNR) of the digital modulated signals. Inparticular, the digital modulated signals may be scaled proportionallyto their respective SNR so that the SNR of the combined modulated signalis maximized. The DSP module 110 may further demodulate the combinedmodulated signal into a single combined digital audio signal. Thecombined digital audio signal may be output on any of the digital audiooutputs. Further details of how the DSP module 110 can combine thedigital modulated signals are described below with respect to FIGS. 5and 6. The DSP module 110 may further include an audio signal processingmodule to further process the digital audio signals prior to beingoutput from the receiver 100.

The digital audio signals output by the receiver 100, including thecombined digital audio signal, may conform to the Audio EngineeringSociety AES3 standard, Dante standard, and/or AVB/AVNU standard fortransmitting audio over Ethernet, for example. Moreover, the receiver100 may output the digital audio signals on an XLR connector output, onan Ethernet port, or on other suitable types of outputs. The analogaudio signals may be output by the receiver 100 on an XLR connectoroutput, a ¼″ audio output, and/or other suitable types of outputs.

The receiver 100 may be rack mountable, and may include a display fordisplaying various information, full audio meters, and RF signalstrength indicators, and may further include control switches, buttons,and the like for user control and setting of configuration options. TheRF ports 102 a-d may be BNC, SMA (SubMiniature version A) coaxialconnectors, N-type, or other suitable connectors for connecting toexternal antennas and/or cabling.

FIG. 2 is a schematic diagram of an antenna distribution module 104 ofthe wireless audio receiver 100 of FIG. 1. The antenna distributionmodule 104 may receive RF signals from antennas connected to the RFports 102 a-d and selectively route the received RF signals to RF analogprocessing modules 106 a-d, and in particular to RF signal processingpaths 302 a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b within theRF analog processing modules 106 a-d. The RF signal processing paths 302a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b are denoted in FIGS.2-3 as RF Channels 1 a, 1 b, 2 a, 2 b, 3 a, 3 b, 4 a, 4 b, respectively,and are shown with dotted lines in FIG. 2 because they are notcomponents of the antenna distribution module 104. Instead, the RFsignal processing paths are shown in FIG. 2 to denote where the antennadistribution module 104 may route the received RF signals, depending onthe mode of the receiver 100. In a cascade mode of the receiver 100, theantenna distribution module may receive RF signals from antennasconnected to the RF ports 102 a, 102 b, route the received RF signals toRF analog processing paths 302 a, 302 b, 304 a, 304 b, 306 a, 306 b, 308a, 308 b (RF Channels 1 a, 1 b, 2 a, 2 b, 3 a, 3 b, 4 a, 4 b), and alsoroute the received RF signals to be output on RF ports 102 c, 102 d (AntC/Cascade A and Ant D/Cascade B), respectively.

As shown in FIG. 2, the antenna distribution module 104 includescomponents to process and route each of the received RF signals. Theprocessing paths of the antenna distribution module 104 are similar foreach of the received RF signals except that RF ports 102 c, 102 d (AntC/Cascade A and Ant D/Cascade B) are connected to switches 221, 231 tosupport the output of RF signals from RF ports 102 a, 102 b in a cascademode of the receiver 100. In a non-cascade mode of the receiver 100, upto four antennas may be connected to the RF ports 102 a-d to receivefour RF signals.

When in non-cascade mode, the RF signals received on RF ports 102 a-d(Ant A-D) may be bandpass filtered by bandpass filters 202, 212, 222,232, respectively, to generate filtered RF signals such that theappropriate frequency bands of the received RF signals are selected. Forexample, the bandpass filters 202, 212, 222, 232 may pass a signal bandfrom 470-636 MHz, 606-801 MHz, 750-952 MHz, and/or other signal bandranges. In the case of the RF signals received on RF ports 102 c, 102 d(Ant C and Ant D), the switches 221, 231 may be configured such that thereceived RF signals are passed through to the bandpass filters 222, 232,respectively, when the receiver 100 is in a non-cascade mode. Thefiltered RF signals may be received by attenuators 204, 214, 224, 234that adjust the gain of the filtered RF signals to produce attenuatedfiltered RF signals. The attenuators 204, 214, 224, 234 may be variableand controlled based on power signals received from RF power detectors203, 213, 223, 233, respectively. The RF power detectors 203, 213, 223,233 may detect the power of each of the received RF signals. Amplifiers206, 216, 226, 236 may receive the attenuated filtered RF signals andprovide low noise gain to produce amplified RF signals.

Each of the amplified RF signals may be split by 2-way splitters 208,218, 228, 238, as shown in FIG. 2. For the Ant A and Ant B processingpaths, the 2-way splitters 208, 218 split the respective amplified RFsignal to 4-way splitters 210, 220, respectively, and to attenuators209, 219, respectively. The signals sent to the attenuators 209, 219 maybe output on ports 102 c, 102 d when the receiver 100 is in cascade modethrough appropriately switching the switches 221, 231.

The amplified signals sent to the 4-way splitters 210, 220 for the Ant Aand Ant B processing paths are further split for potential routing tothe RF signal processing paths 302 a, 302 b, 304 a, 304 b, 306 a, 306 b,308 a, 308 b, depending on the mode of the receiver 100. For the Ant Cand Ant D processing paths (in non-cascade mode), the 2-way splitters228, 238 split the respective amplified RF signal to switches 250, 251,252, 253 for potential routing to RF signal processing paths 306 a, 306b, 308 a, 308 b, also depending on the mode of the receiver 100.

In particular, the amplified RF signal from the amplifier 206 for Ant Ais always routed to RF signal processing paths 302 a, 304 a (RF Channels1 a, 2 a, respectively), and is routed to switches 250, 252 forpotential routing to RF signal processing paths 306 a, 308 a (RFChannels 3 a, 4 a, respectively). Similarly, the amplified RF signalfrom the amplifier 216 for Ant B is always routed to RF signalprocessing paths 302 b, 304 b (RF channels 1 b, 2 b, respectively), andis routed to switches 251, 253 for potential routing to RF signalprocessing paths 306 b, 308 b (RF Channels 3 b, 4 b, respectively).

The amplified RF signals from the amplifier 226 for Ant C are routed toswitches 250, 252 for potential routing to RF signal processing paths306 a, 308 a (RF Channels 3 a, 4 a, respectively), and the amplified RFsignals from the amplifier 236 for Ant D are routed to switches 251, 253for potential routing to RF signal processing paths 306 b, 308 b (RFChannels 3 b, 4 b, respectively). The switches 250, 251, 252, 253 areappropriately switched, depending on the mode of the receiver. Inparticular, switches 250, 251, 252, 253 may be respectively connected tothe 4-way splitters 210, 220 when the receiver is in a cascade mode. Incascade mode, no RF signals are received on the Ant C/Cascade A or AntD/Cascade B ports. As such, RF signal processing paths 306 a, 308 a (RFChannels 3 a, 4 a, respectively) would receive the RF signals receivedon the Ant A port. RF signal processing paths 306 b, 308 b (RF channels3 b, 4 b, respectively) would receive the RF signals received on the AntB port.

FIG. 3 is a schematic diagram of the RF analog processing modules 106a-d of the wireless receiver 100 of FIG. 1. Each RF analog processingmodules 106 a-d may include two parallel RF signal processing paths 302a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b for processing therouted RF signals from the antenna distribution module 104 to generateanalog modulated signals that have been shifted to an intermediatefrequency (IF). In particular, RF analog processing module 106 a (RFChannel 1) may include RF signal processing paths 302 a, 302 b (RFChannels 1 a, 1 b) that always receive RF signals that are routed fromRF port 102 a (Ant A, as denoted by “1A” from 4-way splitter 210) andfrom RF port 102 b (Ant B, as denoted by “1B” from 4-way splitter 220).Similarly, RF analog processing module 106 b (RF Channel 2) may includeRF signal processing paths 304 a, 304 b (RF Channels 2 a, 2 b) thatalways receive RF signals that are routed from RF port 102 a (Ant A, asdenoted by “2A” from 4-way splitter 210) and from RF port 102 b (Ant B,as denoted by “2B” from 4-way splitter 220).

The RF signals routed to RF analog processing modules 106 c, 106 d (RFChannels 3 and 4) may vary, however, depending on the mode of thereceiver 100. RF analog processing module 106 c (RF Channel 3) mayinclude RF signal processing paths 306 a, 306 b (RF Channels 3 a, 3 b)that received RF signals routed through the switches 250, 251,respectively. Switch 250 may route to RF signal processing path 306 a(RF Channel 3 a) the RF signal from RF port 102 a (Ant A, as denoted by“3A” from 4-way splitter 210) or the RF signal from RF port 102 c (AntC, as denoted by “1C” from 2-way splitter 228). Switch 251 may route toRF signal processing path 306 b (RF Channel 3 b) the RF signal from RFport 102 b (Ant B, as denoted by “3B” from 4-way splitter 220) or the RFsignal from RF port 102 d (Ant D, as denoted by “1D” from 2-way splitter238). In a similar fashion, switch 252 may route to RF signal processingpath 308 a (RF Channel 4 a) the RF signal from RF port 102 a (Ant A, asdenoted by “4A” from 4-way splitter 210) or the RF signal from RF port102 c (Ant C, as denoted by “2C” from 2-way splitter 228). Switch 253may route to RF signal processing path 308 b (RF Channel 4 b) the RFsignal from RF port 102 b (Ant B, as denoted by “4B” from 4-way splitter220) or the RF signal from RF port 102 d (Ant D, as denoted by “2D” from2-way splitter 238).

Each of the RF analog processing modules 106 a-d may include a localoscillator (or synthesizer) 350 a-d that generates appropriatefrequencies to be applied to mixers to shift the frequency of the routedRF signals to the desired IF. The signals generated by the localoscillators 350 a-d may be amplified and driven by drivers 352 a-d,respectively, then split by 2-way splitters 354 a-d, respectively, to beapplied to the mixers in the individual RF signal processing paths 302a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b. The analog modulatedsignals at the IF generated by each of the RF signal processing paths302 a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b may be convertedinto digital modulated signals by analog-to-digital converters (ADC) 108a-d. The analog-to-digital converters 108 a-d are depicted as dual ADCsthat output parallel digital modulated signals, but separate, quad,and/or octal ADCs may also be utilized, for example. The components ofthe RF signal processing paths 302 a, 302 b, 304 a, 304 b, 306 a, 306 b,308 a, 308 b are described in more detail with respect to FIG. 4. Itshould be noted that while FIG. 3 depicts that the RF signal processingpaths 302 a, 302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 bd sharerespective local oscillator 350 a-d, it is contemplated and possiblethat the RF signal processing paths may be independent, in someembodiments.

FIG. 4 is a schematic diagram of the components of each of an RF analogprocessing path 400, which includes RF analog processing paths 302 a,302 b, 304 a, 304 b, 306 a, 306 b, 308 a, 308 b of RF analog processingmodules 106 a-d. An RF signal routed by the antenna distribution module104 is received by the RF analog processing path 400 and processed toproduce an IF signal to be transmitted to analog-to-digital converters108 a-d. In particular, a track tuning filter 402 receives the routed RFsignal so that only certain frequencies are passed through to the mixer404. The mixer 404 may heterodyne the filtered signal generated by thetrack tuning filter 402 and generate an IF signal based on a localoscillator signal. The mixer 404 may shift the frequency of the filteredsignal to a desired IF by applying the signal from one of the localoscillators 350 a-d to the filtered signal. The IF signal may then beprocessed by a low noise amplifier 406, IF filter 408, attenuator 410,amplifiers 412, 414, IF filter 416, and low pass filter 418 toultimately generate the analog modulated signal at the IF. The IFfilters 408, 416 may be surface acoustic wave (SAW) filters, in someembodiments.

FIG. 5 is a schematic diagram of a digital signal processing (DSP)module 500 for use in the wireless audio receiver 100 of FIG. 1. The DSPmodule 500 may combine the digital modulated signals from the ADCs 108a-d into a combined modulated signal, based on the signal-to-noiseratios (SNR) of the digital modulated signals. In particular, thedigital modulated signals may be scaled proportionally to theirrespective SNR so that the SNR of the combined modulated signal ismaximized. The DSP module 500 may further demodulate the combinedmodulated signal into a single combined digital audio signal.

FIG. 7 is a schematic diagram of a digital signal processing (DSP)module 700 for use in the wireless audio receiver 100 of FIG. 1. The DSPmodule 700 may combine pairs of the digital modulated signals from theADCs 108 a-d into four combined modulated signals, based on thesignal-to-noise ratios (SNR) of the digital modulated signals. Inparticular, the digital modulated signals may be scaled proportionallyto their respective SNR so that the SNR of the four combined modulatedsignals are maximized. The DSP module 500 may further demodulate each ofthe four combined modulated signals into four digital audio signals.

A process 600 that may perform the combining of the digital modulatedsignals using the DSP modules 500 and 700 is shown in FIG. 6. Thedigital modulated signals from the ADCs 108 a-d may be received bydetectors 502 a-d or 702 a-d, respectively. In some embodiments, thedetectors 502 a-d and 702 a-d may measure the normalized noise power ofeach digital modulated signal (i.e., the noise power relative to unityRMS signal power) by detecting the degree to which pilot symbolsembedded in the digital modulated signals are perturbed from their knownlocations. As such, the detectors 502 a-d and 702 a-d may detect pilotsymbols in the received digital modulated signal (y), such as at step602 of the process 600 shown in FIG. 6. The pilot symbols may have beenembedded in the digital modulated signals by the wireless transmitter.In some embodiments, the pilot symbols may be QPSK symbols arranged inthree symbol blocks, occurring approximately every 125 microseconds. Thegrouping and the rate of the pilot symbols may depend on various signalpropagation characteristics. For example, very slow fading may allow therate of the pilot symbols to be lesser.

A channel estimate (h) of the digital modulated signals may be derived,such as at step 604. The channel estimate may be derived based on thedetected pilot symbols, in some embodiments. Next, the normalized noisepower (σ²) of each of the digital modulated signals may be measured,such as at step 606 of the process 600. In some embodiments, thenormalized noise power may be measured based on the detected pilotsymbols. A normalized received signal may be derived based on thedetected channel estimate, such as at step 608. In the case of theembodiment shown in FIG. 5, a combined modulated signal may be generatedby an SNR maximizing combiner module 504, such as at step 610, based onthe normalized noise power and the normalized received signal. For theembodiment shown in FIG. 7, four combined modulated signals may begenerated by respective SNR maximizing combiner modules 704 a-d, such asat step 610, based on the normalized noise power and the normalizedreceived signal. In some embodiments, the combined modulated signal({circumflex over (X)}) may be generated based on the equation

${\hat{x} = \frac{\sum\limits_{i = 0}^{L - 1}{\frac{h_{i}^{*}y_{i}}{{h_{i}}^{2}}\frac{1}{\sigma_{N_{i}}^{2}}}}{\sum\limits_{i = 0}^{L - 1}\frac{1}{\sigma_{N_{i}}^{2}}}},$where L is the number of digital modulated signals, σ_(N) _(i) ² is thenormalized noise variance/power for input i, h_(i) is the channelestimate for input i, and y_(i) is the received signal for input i.

In the case of the embodiment shown in FIG. 5, the combined modulatedsignal may be demodulated by a decoder module 506 to generate a combineddemodulated signal. The combined demodulated signal may be furtherprocessed by an audio signal processing module 508 to generate acombined digital audio signal. In the case of the embodiment shown inFIG. 7, the four combined modulated signals may be respectivelydemodulated by separate decoder modules 706 a-d to generate fourdemodulated signals. The four demodulated signals may each be furtherprocessed by audio signal processing modules 708 a-d to generate fourdigital audio signals. The audio signal processing modules 508, 708 a-dmay perform, for example, filtering, gain, metering, and/or signallimiting on the combined demodulated signal. The combined digital audiosignal (or separate digital audio signals) may be output by the receiver100, and/or DACs 112 a-d may convert the combined digital audio signal(or separate digital audio signals) to a combined analog audio signal(or separate analog audio signals).

It should be noted that FIGS. 3-7 are exemplary of possible downstreamprocessing modules and methods for processing the received RF signals,and that other schemes and methods of processing received RF signals arepossible. For example, the RF signals may contain analog modulated audiosignals such that the downstream processing modules may include analogdemodulation modules and the like. As another example, the RF signalsmay be directly sampled by downstream processing modules.

Any process descriptions or blocks in figures should be understood asrepresenting modules, segments, or portions of code which include one ormore executable instructions for implementing specific logical functionsor steps in the process, and alternate implementations are includedwithin the scope of the embodiments of the invention in which functionsmay be executed out of order from that shown or discussed, includingsubstantially concurrently or in reverse order, depending on thefunctionality involved, as would be understood by those having ordinaryskill in the art.

This disclosure is intended to explain how to fashion and use variousembodiments in accordance with the technology rather than to limit thetrue, intended, and fair scope and spirit thereof. The foregoingdescription is not intended to be exhaustive or to be limited to theprecise forms disclosed. Modifications or variations are possible inlight of the above teachings. The embodiment(s) were chosen anddescribed to provide the best illustration of the principle of thedescribed technology and its practical application, and to enable one ofordinary skill in the art to utilize the technology in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the embodiments as determined by the appendedclaims, as may be amended during the pendency of this application forpatent, and all equivalents thereof, when interpreted in accordance withthe breadth to which they are fairly, legally and equitably entitled.

The invention claimed is:
 1. A digital signal processor configured to combine a plurality of digital modulated signals (y) based on a signal-to-noise ratio (SNR) of each of the plurality of digital modulated signals, the plurality of digital modulated signals respectively derived from a plurality of received radio frequency (RF) signals each comprising a digital audio bit stream representing an audio signal, the digital signal processor comprising: a detector configured to: derive a channel estimate (h) of each of the plurality of digital modulated signals; measure a normalized noise power (σ²) of each of the plurality of digital modulated signals; and derive a normalized received signal based on the channel estimate; and an SNR maximizing combiner configured to: combine the plurality of digital modulated signals to produce a combined modulated signal based on the normalized noise power and the normalized received signal.
 2. The digital signal processor of claim 1, wherein the SNR maximizing combiner is configured to combine the plurality of digital modulated signals by combining the plurality of digital modulated signals to produce the combined modulated signal based on the equation: ${\hat{x} = \frac{\sum\limits_{i = 0}^{L - 1}{\frac{h_{i}^{*}y_{i}}{{h_{i}}^{2}}\frac{1}{\sigma_{N_{i}}^{2}}}}{\sum\limits_{i = 0}^{L - 1}\frac{1}{\sigma_{N_{i}}^{2}}}},$ wherein L comprises a number of the plurality of digital modulated signals, σ_(N) _(i) ² is the normalized noise variance/power for input i, h_(i) is the channel estimate for input i, and y_(i) is the received signal for input i.
 3. The digital signal processor of claim 1: wherein the detector is further configured to detect one or more pilot symbols in each of the plurality of digital modulated signals; and wherein the detector is configured to: derive the channel estimate by deriving the channel estimate of each of the plurality of digital modulated signals based on the detected pilot symbols; and measure the normalized noise power by measuring the normalized noise power of each of the plurality of digital modulated signals based on the detected pilot symbols.
 4. The digital signal processor of claim 3, wherein the detector is configured to derive the channel estimate by detecting a degree of perturbation of the detected pilot symbols from the known locations of the pilot symbols embedded in each of the plurality of digital modulated signals.
 5. The digital signal processor of claim 3, wherein the one or more pilot signals comprise QPSK symbols arranged in three symbol blocks that occur approximately every 125 microseconds.
 6. The digital signal processor of claim 1, further comprising: a decoder module configured to demodulate the combined modulated signal to a combined demodulated signal; and an audio signal processor configured to process the combined demodulated signal to a combined digital audio signal.
 7. The digital signal processor of claim 6, wherein the audio signal processor is configured to process the combined demodulated signal by one or more of filtering, applying a gain, metering, or signal limiting the combined demodulated signal.
 8. The digital signal processor of claim 6, further comprising a digital to analog converter configured to generate a combined analog audio signal based on the combined digital audio signal.
 9. The digital signal processor of claim 1, further comprising: a decoder module configured to demodulate the combined modulated signal to a demodulated signal; and an audio signal processor configured to process the demodulated signal to a digital audio signal.
 10. The digital signal processor of claim 9, wherein the audio signal processor is configured to process the demodulated signal by one or more of filtering, applying a gain, metering, or signal limiting the demodulated signal.
 11. The digital signal processor of claim 9, further comprising a digital to analog converter configured to generate an analog audio signal based on the digital audio signal.
 12. The digital signal processor of claim 1, wherein the normalized noise power comprises a noise power of each of the plurality of digital modulated signal relative to unity RMS signal power. 